Are these the pointy euro fuses? Take a look at a used fuse, there will be a thin ring where the fuse makes contact with the fuse block. This is the only area where current flows.

I've used the edge of a single edge razor blade to clean the hole in the terminal as that is the only area that matters.

Some fuses use a plastic body rather than the old ceramic, the plastic ones tend to melt at high current levels resulting in a loose fuse. I've even gone so far as to swap the element to a ceramic body.

My 1980 SAAB 900 has these and they are a pain to keep clean even though the fuse block is covered.

The irony here is that most of the OE ceramic-body fuses I've run across, have aluminum elements - not such a great thing when they start to corrode after prolonged contact with the copper strips in the fusebox. And while most aftermarket fuses have copper elements, too many use plastic bodies that melt under heavy load!
All things considered, I prefer the OE fuses to the plastic aftermarkets, and often grab a few spare OE fuses (if they're in decent shape and not too corroded) when I visit local salvage-yards.

I do think the best combination is having the copper elements on ceramic bodies, so I've done the element-swap trick a couple times. One was on the blower circuit of my first 240D, (a common problem on W123s) which kept melting the plastic fuses.

Happy Motoring, Mark

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DrDKW